arch/x86/lib/cmdline.c

Source file repositories/reference/linux-study-clean/arch/x86/lib/cmdline.c

File Facts

System
Linux kernel
Corpus path
arch/x86/lib/cmdline.c
Extension
.c
Size
5270 bytes
Lines
236
Domain
Architecture Layer
Bucket
arch/x86
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

switch (state) {
		case st_wordstart:
			if (!c)
				return 0;
			else if (myisspace(c))
				break;

			state = st_wordcmp;
			opptr = option;
			wstart = pos;
			fallthrough;

		case st_wordcmp:
			if (!*opptr) {
				/*
				 * We matched all the way to the end of the
				 * option we were looking for.  If the
				 * command-line has a space _or_ ends, then
				 * we matched!
				 */
				if (!c || myisspace(c))
					return wstart;
				/*
				 * We hit the end of the option, but _not_
				 * the end of a word on the cmdline.  Not
				 * a match.
				 */
			} else if (!c) {
				/*
				 * Hit the NULL terminator on the end of
				 * cmdline.
				 */
				return 0;
			} else if (c == *opptr++) {
				/*
				 * We are currently matching, so continue
				 * to the next character on the cmdline.
				 */
				break;
			}
			state = st_wordskip;
			fallthrough;

		case st_wordskip:
			if (!c)
				return 0;
			else if (myisspace(c))
				state = st_wordstart;
			break;
		}
	}

	return 0;	/* Buffer overrun */
}

/*
 * Find a non-boolean option (i.e. option=argument). In accordance with
 * standard Linux practice, if this option is repeated, this returns the
 * last instance on the command line.
 *
 * @cmdline: the cmdline string
 * @max_cmdline_size: the maximum size of cmdline
 * @option: option string to look for
 * @buffer: memory buffer to return the option argument
 * @bufsize: size of the supplied memory buffer
 *
 * Returns the length of the argument (regardless of if it was
 * truncated to fit in the buffer), or -1 on not found.
 */
static int
__cmdline_find_option(const char *cmdline, int max_cmdline_size,
		      const char *option, char *buffer, int bufsize)
{
	char c;
	int pos = 0, len = -1;
	const char *opptr = NULL;
	char *bufptr = buffer;
	enum {
		st_wordstart = 0,	/* Start of word/after whitespace */
		st_wordcmp,	/* Comparing this word */
		st_wordskip,	/* Miscompare, skip */
		st_bufcpy,	/* Copying this to buffer */
	} state = st_wordstart;

	if (!cmdline)
		return -1;      /* No command line */

	/*
	 * This 'pos' check ensures we do not overrun
	 * a non-NULL-terminated 'cmdline'

Annotation

Implementation Notes